In 1915, leaders in Miami -- then still a sleepy Southern outpost but growing fast -- considered paying an outside expert to devise a master plan to guide future development.

But the $1,500 price tag was deemed too expensive, so the city passed.

''What a lost opportunity,'' Miami Mayor Manny Diaz now says. "We could be living in a very different city today.''

Diaz has spent the past couple years crusading for his own city master plan, this one costing taxpayers $1.7 million. And just as in 1915, there are naysayers.

Could the effort go down in flames again?

A key indicator will come Thursday, when Miami City Commissioners are set to hold the first of two required votes on the first phase of Miami 21 -- Diaz's brainchild.

The Miami 21 plan would rewrite the zoning code in many of the city's eastern neighborhoods, with other parts of town to follow in the coming months. The plan encourages mixed-use, pedestrian-friendly streets and town centers with shaded, wider sidewalks. Miami 21 also promises to simplify the city's zoning code -- though skeptics, citing its creation of a whole new city zoning vocabulary, question whether that has been achieved.

One thing is for sure: The plan has done the seemingly impossible by uniting some neighborhood activists with development interests.

A significant number of folks in both camps strongly dislike the plan. ''So there's obviously something wrong with this picture,'' neighborhood activist Beba Mann said.
"There's a lot of things that still need to be addressed and covered.''

Some homeowners cringe at portions of the plan that would reduce the number of public hearings new developments are required to go through -- limiting opportunities for public input.

Developers, meanwhile, fear some of the proposed zoning changes will force them to design smaller buildings than are allowed under current code. Another developer complaint: Under Miami 21, it's difficult to figure out what can be built on a certain property without the aid of an architect.

Some architects, too, are unhappy. The architectural firm Miami hired to write Miami 21 -- the world-renowned, Miami-based Duany Plater-Zyberk and Co. -- is both famous and controversial.

The company's New Urbanist architecture stresses uniformity and predictability for new construction. Mayor Diaz said this will be welcome news for a city now stuck with myriad and sometimes conflicting zoning guidelines. Diaz also said a sense of order is exactly what some of the city's hodge-podge neighborhoods need.

But one person's ''predictable'' architecture is another person's cookie-cutter. Real estate developer Matthew Greer of The Carlisle Group, an affordable-housing developer, says Miami 21's approach offers transparency, but
"it remains to be seen whether a heterogeneous, dynamic environment like Miami is the right ecosystem for that type of planning system to take root.''

City Commissioner Marc Sarnoff said he hasn't made up his mind and is willing to give the plan a chance during Thursday's meeting.